Marvin vs Skylos

Side-by-side comparison of features, pricing, and ratings

Analysis reviewed Live tool data as of 2026-10-08
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At a glance

DimensionMarvinSkylos
IntegrationOpenAI, AnthropicGitHub Actions, Slack, Discord, VS Code, Claude Code, Cursor, MCP
Primary UseBuild LLM-powered apps (chat, extraction, classification)Static analysis for Python code (dead code, secrets, AI mistakes)
Target UserPython developers adding AI to existing codePython developers using AI coding agents (Claude Code, Cursor)
Key Feature@ai_fn and @ai_classifier decorators for type-safe LLM callsDetects hallucinated imports, phantom calls, and removed controls from AI-generated code
Not ForNon-developers or frontend-only developersTeams needing multi-language SAST or no CLI usage

Pick Marvin if you're a Python developer who wants to embed LLM-driven features (chat, classification, extraction) directly into your app with minimal boilerplate. Pick Skylos if you're a Python developer using AI coding assistants and need a tight PR gate that catches dead code, secrets, and AI-specific bugs like hallucinated imports and removed security controls before merge. They solve completely different problems — one builds with LLMs, the other audits what LLMs wrote.

Try MarvinTry Skylos
Marvin
Marvin

Marvin is an open-source Python framework that turns ordinary functions into AI-powered tools using decorators like @ai_fn and @ai_classifier.

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Skylos
Skylos

Skylos is a local-first Python static analysis CLI that catches dead code, secrets, and AI-code mistakes before they merge.

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Pricing
Free
Freemium
Plans
$0/mo
$0
$0
$9 / 50 credits
Custom
Popularity
7.1k views
10 views
Skill Level
Intermediate
Intermediate
API Available
Platforms
CLI
CLIAPI
Categories
📦 LLM App Frameworks & SDKs
🔎 Code Review & Quality🔐 Application & Code Security
Features
marvin.run() for one-line task execution
@ai_fn decorator for AI-powered functions
@ai_classifier decorator for text classification
Structured output via Pydantic result_type
Named Agent objects with custom instructions
marvin.Memory for persistent cross-conversation memory
Multi-agent coordination and chaining
MCP (Model Context Protocol) server support
Streaming output support
Async-first API
Built-in task results and memory management
Rate limiting and retries
Concurrency control
SQLite state store
CLI interactivity mode
Dead code detection for unused functions, imports, classes, and variables
SQL injection detection that traces tainted input into string-built queries
Command injection detection for unsafe shell execution paths
Hardcoded secrets detection with provider labels (AWS, Stripe) and masked previews
AI-defect detection for hallucinated imports, invented APIs, and phantom calls
Removed security control detection (auth decorators, CSRF checks, rate limits)
Software composition analysis with package reachability and fix versions
Smart Tracing: runs your test suite to eliminate dead-code false positives
Diff review that flags risky changes before merge
GitHub Actions PR gate and CI merge gate
VS Code extension for in-editor findings
MCP server support for agent remediation workflows
Cloud Workspace: stored scans, comparisons, PR comments, and shared triage
Multi-language analysis for Python, JavaScript/TypeScript, Go, Java, Kotlin, PHP, Rust, Dart, C#, and Shell
Local-first scan with no code upload and no login
Integrations
OpenAI
Anthropic
GitHub Actions
VS Code
Slack
Discord
Claude Code
Cursor
MCP

What real users say: Marvin vs Skylos

Not marketing copy and not our opinion — a structured sweep of public discussion (reviews, forums, communities and video comments), showing what people praise and what they complain about for each tool.

Marvin

90 mentions across 7 sources · 29% positive — critical (averaged across 7 sources)

Hacker News, YouTube, Product Hunt, Bluesky, Stack Overflow, GitHub, Lemmy

What users praise

  • • Decorator-based API simplifies LLM integration for Python devs.
  • • Local execution gives full data control and no cloud lock-in.
  • • Supports OpenAI and Anthropic models with minimal configuration.
  • • Pydantic integration enables type-safe structured data extraction.

What frustrates them

  • • No real community feedback to validate reliability or usefulness.
  • • 110 open GitHub issues may indicate unresolved bugs.
  • • Azure OpenAI integration reported broken by multiple users.
  • • Documentation examples may not work as described (audio.speak bug).

Researched Jul 24, 2026

Skylos

35 mentions across 4 sources · 52% positive — mixed (averaged across 4 sources)

Hacker News, YouTube, GitHub, Lemmy

What users praise

  • • Dead code detection beats Vulture (29/29 vs 24/29) on real libraries.
  • • Local-first CLI with no login requirement offers quick, private testing.
  • • Unique focus on AI-code mistakes like hallucinated imports and phantom calls.
  • • Integrates with Claude Code, Cursor, GitHub Actions, VS Code, and MCP.

What frustrates them

  • • False positives on decorators, TypedDict fields, and closure parameters.
  • • Internal package imports incorrectly flagged as undeclared (SKY-D223).
  • • macOS terminal probing breaks the TUI progress display.
  • • Interactive remove/comment-out fails in WSL2 environments.

Researched Aug 29, 2026

Who should pick which

  • Python developer building an LLM-powered data extraction pipeline
    Pick: Marvin

    Marvin's @ai_fn with Pydantic models gives type-safe structured outputs with minimal code, ideal for extraction tasks.

  • Developer using Claude Code to generate Python code and worried about AI hallucinations
    Pick: Skylos

    Skylos specifically detects hallucinated imports, phantom calls, and removed controls — exactly the bugs AI coders introduce.

  • Open-source maintainer wanting to clean up dead code in a Python repo
    Pick: Skylos

    Skylos offers low false positives (98.1% recall, 21× fewer false positives than Vulture on Flask) and a PR gate.

  • Solo developer prototyping a chatbot with minimal infrastructure
    Pick: Marvin

    Marvin's decorators and built-in streaming let you quickly build a chatbot without managing cloud services.

  • DevOps engineer setting up a Python PR quality gate
    Pick: Skylos

    Skylos integrates with GitHub Actions, has tokenless CI, and can block high-confidence regressions — fits a CI pipeline.

Frequently Asked Questions

Marvin vs Skylos: which should you choose?

Pick Marvin if you're a Python developer who wants to embed LLM-driven features (chat, classification, extraction) directly into your app with minimal boilerplate. Pick Skylos if you're a Python developer using AI coding assistants and need a tight PR gate that catches dead code, secrets, and AI-specific bugs like hallucinated imports and removed security controls before merge. They solve completely different problems — one builds with LLMs, the other audits what LLMs wrote.

Can Marvin be used for non-AI tasks?

No, Marvin is specifically for adding LLM capabilities to Python functions — it doesn't do static analysis or code quality checks.

Does Skylos support languages other than Python?

Skylos is Python-focused; other languages are limited. If you need multi-language SAST, consider alternatives like Semgrep or CodeQL.

Can I use Marvin without writing any code?

No, Marvin requires Python development — it's a framework, not a no-code tool. Non-developers should look elsewhere.

Does Skylos require uploading my code to use it?

Local scans run without upload. Cloud features (shared triage, history) require uploading code to the Cloud workspace.

Does Marvin support any LLM provider besides OpenAI and Anthropic?

The provided data only mentions OpenAI and Anthropic. Other models may be supported via custom integrations, but it's not documented.

Is Skylos a replacement for Semgrep or CodeQL?

Not exactly — Skylos complements them with focus on AI-specific defects and dead code, but it's Python-focused and not a full SAST platform.

Can Marvin be used in production without managing infrastructure?

Marvin runs in your own environment, so you do manage infrastructure. For a hosted alternative, consider other managed services.

Does Skylos have a VS Code extension?

Yes, Skylos integrates with VS Code, as well as Claude Code, Cursor, and MCP servers.

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Explore each tool further

Marvin
View Marvin reviewMarvin alternatives
Skylos
View Skylos reviewSkylos alternatives

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Best AI LLM App Frameworks & SDKs toolsBest AI Code Review & Quality toolsBest AI Application & Code Security tools
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Last reviewed: July 30, 2026